JPS6352976A - Method of clamping bolt - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a bolt tightening method for tightening a bolt to a value close to its elastic limit.

(Prior art) Conventionally, as a bolt tightening method, for example,
There is a constant torque tightening method described in JP-A-58272.

This tightening method is a method of applying a constant torque to tighten the bolt within its elastic limit, but this conventional method has the disadvantage that the tightening axial force varies greatly due to fluctuations in the friction coefficient of the bolt.

In order to eliminate such drawbacks, a rotation angle tightening method as shown in FIG. 5 and a seating point angle tightening method as shown in FIG. 6 have been invented.

As shown in Fig. 5, the former rotational angle tightening method is affected by the coefficient of friction up to the snug torque, which is the initial starting point, and when trying to obtain a high tightening axial force P, especially I! Pol i~, which has a low coefficient of friction, had the problem of falling into the yield range.

On the other hand, the latter seating point angle tightening method has the advantage of being unaffected by snagging torque and stabilizing the tightening axial force P;
In particular, bolts with a high coefficient of friction have the problem that, as is clear from FIG. 6, the angle from the seating point to yielding is small, and the tightening axial force P becomes a relatively low value.

(Objective of the Invention) This invention can significantly improve the variation in tightening force compared to the conventional torque method, and can also increase the average axial force compared to the rotation angle method. To provide a bolt tightening method that can stably obtain a tightening axial force within a range in which the bolt does not yield, and that can tighten the bolt at a value close to the yield range.

(Structure of the Invention) This invention calculates a torque rate during tightening of a bolt, calculates a constant tightening torque or a theoretical ground line angle from a seating point in accordance with this torque rate, and based on this calculation result. The present invention is characterized in that it is a bolt tightening method that performs the first corner tightening.

(Effects of the Invention) According to the present invention, the torque rate (conversion of tightening torque to the tightening angle, in other words, l~silk distribution), which corresponds to the friction coefficient, is determined during tightening of the bolt, and this torque For example, calculate the theoretical seating point from the rate, calculate the theoretical ground line angle from this theoretical seating point to the elastic limit point, and based on this calculation result, calculate the angle r! ! Since we are tightening the bolts)! ! Even if the friction coefficient fluctuates, tightening can always be performed along the elastic limit line (yield area) and at a value close to the yield area, and the effect is that the tightening axial force can be stabilized at a high value.

(Example) An embodiment of the present invention will be described in detail below based on the drawings.

First, the theory of the tightening method will be described with reference to FIGS. 3 and 4.

When tightening a bolt, the higher the friction coefficient μ of the threaded portion, the lower the tightening axial force P will cause yielding. This is because torsional stress acts on the bolt as well as tensile stress, and this torsional stress is expressed by the following equation.

T: Tightening torque, dl: Valley diameter dimension d: Effective diameter dimension, P: Tightening axial force μ: Friction coefficient, β: Screw lead angle From the above formula, the bolt has a high friction coefficient μ, torsional stress τ
It is clear that a low tightening axial force P leads to yielding, and since this tightening axial force P is proportional to the tightening angle θ, a bolt with a high Bv coefficient μ of the threaded portion will not seat properly. The angle from the point that enters the yield region becomes small.

That is, in order to obtain a high axial force P within the elastic range limit of the bolt, it is optimal to control the tightening angle 11 according to the friction coefficient μ.

Since the friction coefficient μ and the torque rate described above are in a corresponding relationship, this torque rate is determined during the tightening of the bolt.

That is, for bolt A in FIG. 3, the torque rate can be calculated from both the tightening torque T - T1 during tightening and the tightening angle θ2-01 using the following equation.

△Torque rate of bolt = (T - T ) / (θ2 - 01) Similarly, the tightening torque T -■ and the tightening angle θ2 during tightening of bolt B in Fig. 3. -01, and the torque rate can be calculated from the following equation.

Torque rate of B bolt = (T - T )/<02" 1.) Also, the theoretical seating point θ is determined from the torque gradient of each characteristic in Figure 3, and from this theoretical seating point θ, the elastic limit point of each port is determined. The theoretical ground line angles θΔ and θB up to P1 and P2 are calculated, and angle tightening is performed based on the theoretical ground line angles θΔ and θB.

The above-mentioned logical ground line angles OA and θB can be obtained from the following equations.

Torque rate of θΔ-/A bolt θB=to/B bolt torque rate However, K is a tightening coefficient.

FIG. 1 is a block diagram of a control device used in the bolt tightening method.
On one side, there is an angle encoder 4 that encodes the current angle, and the output of the torque transformer described above is increased by a preamplifier AMP.

The DC nut runner 5 includes a DC motor 3 and a reduction gear device 2.
, a transducer, an angle encoder 4, and a preamplifier AMP.

On the other hand, a first torque setter 6 that sets the seating torque TO, a second torque setter 7 that sets the torque rate detection start torque T1, and a third torque setter 8 that sets the torque rate detection end torque T2. These tortum 2 regulators 6, 7° 8 are connected to the respective first comparator 9, second comparator 10, third comparator 11, first analog switch 12, and second analog switch 1, respectively.
3. The third analog switch 14 is connected to the control circuit 15 through each one separately.

Further, the aforementioned torque transducer 1 is connected via the line 16 to the other input terminal of each of the aforementioned comparators 9, 10° 11 and the fourth analog switch 17, while the aforementioned control circuit 15 is connected via the servo amplifier 18. The above-mentioned DC motor 3 is connected thereto.

Furthermore, a first angle gate 20 and a second angle gate 21 are connected to the angle encoder 4 through one line, and the output stage of one of the first angle gates 20 is connected to an increasing angle through a first counter 22. output circuit 23, and the other second
A waste angle output circuit 25 is connected to the output stage of the angle gate 21 via a second counter 24, respectively.

The increased torque output circuit 26 connected to the output side of the fourth analog switch 17 described above and the increased angle output circuit 23 described above are connected to two computing units via respective lines 27 and 28, and the computing units Torque rate dT at 29
/ dθ, theoretical seating point θ. and theoretical waste angle θΔ, θ
B (see Fig. 3) is constructed in a complex manner.

Furthermore, the theoretical ground wire angle output circuit 30 connected to the output stage of the arithmetic unit 29 in above) E and the waste cotton angle output circuit 2 mentioned above.
5 and a comparator 33 via respective lines 31,32.
is connected to.

In addition, the aforementioned control circuit 15 and each element 17, 18°20.2
1, 22, 29, and 33 are connected to each other via lines 34 to 41.

Next, refer to the flowchart in Figure 2 and tighten the bolts (-
I will explain the method.

In the first step 51, start the nut runner 5,
In the next second step 52, the seating torque T is set by the first torque setting device 6 described above. Set.

The start signal for the nut runner 5 described above is applied to the control circuit 15 via a signal line (not shown), and the control circuit 15 receives the nut runner start signal (not shown).
At step 53, the nerve arm 18 is driven, and at the next fourth step 54, the DC motor 3 is driven.

The bolt is tightened through the reduction gear device 2 by driving the DC motor 3 described above.

Next, in a fifth step 55, the first comparator 9 sets the current tightening torque of 1 herk from the torque transducer 1 and the seating torque preset by the first torque setter 6. Which match,
A mismatch is determined, and the current tightening torque is set to T. When the first analog switch 12 is turned on in the next sixth step 56 by the coincidence output of the first comparator 9 mentioned above,
Set it to N.

By applying this analog switch ON signal to the servo amplifier 18 via the control circuit 15, the servo amplifier 18 stops the nut runner 5 in the next seventh step 57.

Next, in the eighth step 58, the put runner 5 is rotated again, and in the next ninth step 5, the torque rate detection starting torque T1 (see FIG. 3) is set by the second torque setting device 7.

Above) By re-driving the main runners 1 to 5, the current tightening torque from the bolt clamps 1 to 1 is output to the second comparator 10, so at the next 10th step 60,
This second comparator i o i;L determines whether the current tightening torque matches or does not match the torque rate detection start torque T1 set in advance by the second torque setting device 7, and determines whether the current tightening torque is the torque rate detection start torque. When T1 is reached, the coincidence output of the second comparator 10 causes the next 11th
In step 61, the second analog switch 13 is turned on.

This analog switch ON signal is applied to the control circuit 15, and the control circuit 15 turns on the fourth analog switch 17 in the next 12th step 62, and applies an increase of 1 herk to the increase torque output circuit 26 of the next stage. Take in.

Further, in the next 13th step 63, the control circuit 15 closes the first angle gate 20 and sends the increasing angle signal from the angle encoder 4 to the increasing angle output circuit 23 via the first counter 22.
Incorporate into.

Next, in a fourteenth step 64, the third torque setting device 8 sets the torque rate detection end torque T2.

Next, in a fifteenth step 65, the third comparator 11 determines whether the current tightening torque from the torque transducer 1 matches or does not match the torque rate detection end torque T2 preset by the third torque setter 8, and When the current tightening torque reaches the torque rate detection end torque T2, the third analog switch 14 is turned on in the next 16th step 66 based on the coincidence output of the third comparator 11 mentioned above.

This analog switch ON signal is applied to the control circuit 15, and in the next seventeenth step 67, the control circuit 15 turns off both the fourth analog switch 17 and the first angle switch 17-20.

Next, in an 18th step 68, the calculator 29 outputs the increased torque signal T2-T1 from the increased torque output circuit 26 and the increased angle signal from the increased angle output circuit 23, for example, in the case of A volt in FIG. Torque rate dT/dθ=(T-T)/<02-0 based on both θ2-θ1
1) and the theoretical seating point θ. and the theoretical pay increase angle (A in Figure 3)
In the case of a bolt, the angle θA) is calculated.

Next, in the 19th step 6, the theoretical feed increase angle θA as the result of the calculation in above) is taken in as the setting value of the theoretical ground wire angle output circuit 30, and in the 20th step 70, the theoretical feed increase angle θA as the result of the calculation of
5 turns on the second angle gate 21.

When the second angle gate 21 is turned on, the reference ground line angle signal from the angle encoder 4 is taken into the augmented angle output circuit 25 via the second counter 24.

Next, in the 21st step 71, the comparator 33 outputs the theoretical feed increase angle θA as the set value from the theoretical ground line angle output circuit 30,
It is determined whether the current retightening angle matches or does not match the current retightening angle from the retightening angle output circuit 25, and the current retightening angle is determined as the above-mentioned theoretical retightening angle θA.
In other words, when the elastic limit point P1 is reached, the coincidence output of the comparator 33 described above is fed back to the control circuit 15, and in the next step 72, the control circuit 15 controls the DC motor 3 and The nut runner 5 is stopped to finish tightening the bolts, and the second angle gate 21
Turn OFF and complete the series of processing.

In this way, while tightening the bolt, I! i! In the case of the torque rate that corresponds to the IM coefficient, that is, Δvolt in Fig. 3, (T - T ) / (θ2 - θ ),
In the case of B bolt, (T2-T1)/×θ2. -01・
) and find the theoretical seating point θ from this torque rate. At the same time, from this theoretical seating point θ, the elastic limit point P1.
Since this method calculates the theoretical ground line angles OA and θB up to P2 and performs angle tightening based on the calculation results, even if the friction coefficient of the bolt fluctuates, it will always work as shown in Figure 4. It is possible to perform tightening along the i-yield region and at a value close to this yield region, and there is an effect that the tightening axial force can be stabilized at a high value.

Furthermore, this tightening method also allows for tightening in the plastic range, in which the bolt is tightened above its yield point, and the plastic elongation δ and δ2 (see Figure 3) during plastic tightening can be controlled to a constant level. .

As a result, it becomes easy to inspect the amount of plastic elongation during childbirth, and it is also possible to improve reusability and easily ensure a predetermined axial force.

In addition, the above-mentioned tightening method can be applied to the nut rotation angle method and J31 constant torque decagonal one-axis tightening method, and by controlling the tightening angle from a constant torque by the torque rate, it can be applied to the seating point angle method. A similar effect can be obtained.

However, when the initial constant torque is high, the influence of the friction coefficient up to the constant torque becomes large, and the theoretical tightening angle θ becomes the product of Dorkure 1~ and the tightening coefficient.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, FIG. 1 is a block diagram of a control device used in the bolt tightening method, FIG. 2 is a flow chart showing the bolt tightening method, and FIG.
The figure is a characteristic diagram showing the change in torque with respect to the tightening angle. Figure 4 is a characteristic diagram showing the bolt tightening state using the seating point theory tightening angle control method. Figure 5 is a characteristic diagram showing the bolt tightening state using the conventional torque method and constant torque ten angles. FIG. 6 is a characteristic diagram showing the bolt tightening state according to the conventional seating point angle tightening method. 29...Calculator Figure 3 Figure 4 Hourly Torque 7T (91m) Figure 5

Claims (1)

[Claims] 1. Determine the torque rate while tightening the bolt, calculate the constant tightening torque or the theoretical retightening angle from the seating point in accordance with this torque rate, and adjust the angle of the bolt to be tightened based on this calculation result. Tightening method.